On Dec 30 2006, 4:49 pm, indago wrote:
061230 1341 - Furry posted:



Folks,

We have a 1200 sq ft full basement that we're heating via radiant heat.
There are 4 runs of Pex. We're very happy with it but I'm worried that
there is something wrong with the system. When the basement calls for
heat the pump turns on and I can see the temperature gauge go up to
around 100-110 degrees. There's no gauge on the return but feeling the
Pex it's obvious that the water coming back is pretty cool. The
problem: It takes at least an hour, sometimes 2, for the basement to
warm up enough that the thermostat stops calling for heat. 1200 sq ft
is a lot of concrete to heat up but isn't that a long time?

Any thoughts much appreciated.

Thanks, Bill

First of all thanks for your various ideas and feedback. It eventually
became clear that the radiant heat was working just fine - the problem
was the level of insulation in the basement. There wasn't enough
insulation installed on the exterior of the basement foundation when
the house was built, which allowed a lot of the warmth to escape
through the concrete. There was plenty of insulation installed *below*
the radiant heat though. The best solution I've been able to come up
with is to use Owens Corning Formular 250 which is Extruded
Polystyrene Insulation. It comes in 2" X 2' X 8' sheets and is about
$15/sheet. They have an R-10 rating. The stuff is very easy to work
with, all you need is a hand saw to cut it to size.

After putting the Formular 250 up [just stood them up against the
concrete] for just 30 or 40% of the basement wall the time between
reheatings went up from every 4 hours or so to almost 12. Still takes
the same amount of time to heat back up, say 3-4 hours.

So I'm going to complete the job, putting the Formular on as much of
the basement walls as possible. The thing I'm trying to figure out now
is what to use. Is there some sort of caulking or glue that will bind
the Formular to the concrete? I'd like to form as tight a connection
as possible to make sure air and therefore water vapor doesn't get in
behind the insulation and make a great breeding ground for mold. I'm
also going to want to tape the seams. Anyone have any ideas on what
products to use for gluing and taping?

Thanks, Bill